Analytical instruments which utilize infrared absorbence to determine the presence of, or concentration of, a compound or compounds, require a source of infrared light in order to perform analysis. This source, referred to henceforth as an IR (infrared) emitter, typically takes the form of a wire, filament or conductive ceramic element. To activate, the IR emitter is heated by passing electric current through the conductive wire, filament or ceramic element. The current is converted to heat according to the formula that the square of the electrical current multiplied by the xe2x80x9cemitter""sxe2x80x9d resistance is equal to the heat emitted. The infrared emission is proportional to the temperature and surface area of the heated element. Often, it may be desirable or necessary to pulse the infrared emission by interrupting the electrical current periodically to modulate the surface temperature of the element.
Commercially available IR emitters typically suffer one or more of the following shortcomings: high cost; short life; mass may be too high for pulsing; poor mechanical stability; long lead times; and fragility. Packaging may inhibit efficient collection of emissions. They are usually not adjustable by the user. And the resistance to get effective IR emission may be too low to provide efficient drive circuitry.
It is an object of this invention to overcome the shortcomings of the IR emitters currently being used commercially. Specifically, it is an object of this invention to provide an IR emitter that is relatively easy to use and to control by the user and which provides accurate, reproducible results.
The objects are accomplished by employing a surface mount resistor, commonly used as a heat supplier, as an IR emitter for use in analytical instruments.